Gluconeogenesis is a process of major physiological importance in all species, especially in ruminants. The long-term objective of this project is to quantitate the sources contributing to the total glucose utilized by ruminants in various dietary and physiological states. Our standard animals, chosen for the least complicated physiological state, are 160-205 kg calves fed a high grain ration every two hours at levels which will promote slow growth. Our first step was to determine glucose turnover rates in these calves, and much of this was accomplished during 1973. The next steps will be to determine the quantitative contribution to total glucose of absorbed glucose, propionate, and other gluconeogenic compounds such as protein and absorbed lactate. During 1973 we made considerable progress in determining maximum limits for absorbed glucose and studies were begun to guantitate the contribution of propionate. During 1974 major effort will be toward determining the extent of conversion of propionate to glucose. When precursors amounting to total glucose turnover have been quantitated, we will expand to include other diets and animals in other physiological states. When precursors have been quantitated, gluconeogenic pathways will be examined in detail by measuring enzyme activities and metabolite levels in liver and kidney.